In general, an image processing apparatus such as a laser printer includes a photosensitive drum having electrostatic latent images formed thereon, a process cartridge having a developing roller for supplying toner to the photosensitive drum, and a toner cartridge (developer cartridge) having toner accommodated therein. As an example of the image forming apparatus, JP-A-9-319202 discloses a configuration including a supply opening for supplying toner in a toner cartridge to a developing chamber, a toner cartridge having formed therein a return opening for returning toner from the developing chamber to the inside of the toner cartridge, an agitator having blades for agitating the interior of the toner cartridge, and an auger capable of conveying toner within the developing chamber at a supply opening side toward a return opening side. In the image forming apparatus, the toner agitated by the rotation of the agitator is discharged to the developing chamber through the supply opening, conveyed toward the return opening by the auger and then returned to the inside of the toner cartridge through the return opening. Therefore, by circulating the toner in this manner, it may be possible to suppress the toner from being left accumulated in the developing chamber.